fix(inputs): always subtract integration constant when deriving magnetizing current from voltage

The is_continuously_conducting_power heuristic was wrong for pure inductor
mode: a pure inductor has V and I in ~90 degree quadrature, so V*I ~ sin(2wt)
crosses zero often, causing the heuristic to misclassify the load as
discontinuous and skip average subtraction of the integrated voltage waveform.

For harmonic-rich AC excitations (e.g. sinusoidal with high THD), the
integration constant was left in place, producing a unipolar [0, +Imax]
magnetizing current and an asymmetric flux density whose processed.peak equalled
peak-to-peak (Bpeak = 2 x BACpeak in the UI).

Fix: always pass subtractAverage=true in this branch. Any intentional DC bias
is supplied separately via the dcCurrent argument and added back after.

Adds regression test Test_Magnetizing_Current_Pure_Inductor_With_Measured_Current_Is_Bipolar
that verifies the MC is bipolar-centered and peak ~ peakToPeak/2.

Also fixes test data path helper in TestMagneticAdviser.cpp (unrelated cleanup).

Author: AlfVII

src/processors/Inputs.cpp

@@ -2278,8 +2278,24 @@ SignalDescriptor Inputs::calculate_magnetizing_current(OperatingPointExcitation&
         sampledMagnetizingCurrentWaveform = calculate_sampled_waveform(newWaveform, excitation.get_frequency());            
     }
     else {
-        bool subtractAverage = is_continuously_conducting_power(excitation);
-        sampledMagnetizingCurrentWaveform = calculate_integral_waveform(voltageSampledWaveform, subtractAverage);
+        // Always subtract the integration constant: in steady state, a pure
+        // inductor driven by a symmetric AC voltage has zero net DC in the
+        // magnetizing current. The integration of V(t) produces an arbitrary
+        // constant of integration that depends on where the numerical
+        // integration starts within the cycle — for asymmetric / harmonic-rich
+        // waveforms (e.g. distorted "sinusoidal" with high THD) this constant
+        // is non-zero and lopsides the resulting current into a unipolar
+        // [0, +Imax] shape. Any intentional DC bias is supplied separately
+        // via `dcCurrent` and added back below; the integration constant
+        // itself is physically meaningless and must always be removed.
+        //
+        // The previous `is_continuously_conducting_power(excitation)` heuristic
+        // was wrong for inductor mode: a pure inductor has V and I in ~90°
+        // quadrature, so V·I ≈ sin(2ωt) crosses zero often and the heuristic
+        // misclassified the load as discontinuous, leaving the spurious DC in
+        // place. The result was Bpeak = peakToPeak (instead of peakToPeak/2)
+        // for harmonic-rich AC excitations.
+        sampledMagnetizingCurrentWaveform = calculate_integral_waveform(voltageSampledWaveform, true);
         SignalDescriptor magnetizingCurrentExcitation;
 
 

tests/TestInputs.cpp

@@ -1258,6 +1258,66 @@ TEST_CASE("Test_Magnetizing_Current_Sinusoidal_Dc_Bias_Processed", "[processor][
     REQUIRE_THAT(excitation.get_magnetizing_current().value().get_processed().value().get_peak().value(), Catch::Matchers::WithinAbs(expectedValue, max_error * expectedValue));
 }
 
+// Regression: pure-inductor AC excitation with V *and* I both supplied (e.g. a
+// measured / pre-populated current waveform) must still produce a bipolar
+// centered magnetizing current. The previous behaviour fed the excitation into
+// `is_continuously_conducting_power`, which classifies V·I ≈ sin(2ωt) (V & I
+// in ~90° quadrature) as discontinuous because the product spends >10% of the
+// cycle near zero, then suppressed the average-subtraction of the integrated
+// voltage. The integration constant of V(t) was therefore left in place,
+// producing a unipolar [0, +Imax] magnetizing current and an asymmetric flux
+// density whose `processed.peak` was equal to its peak-to-peak (Bpeak =
+// 2 × BACpeak in the UI). See WebFrontend OP3 "HARMONICS" reproducer.
+TEST_CASE("Test_Magnetizing_Current_Pure_Inductor_With_Measured_Current_Is_Bipolar", "[processor][inputs][smoke-test]") {
+    json inputsJson;
+    inputsJson["operatingPoints"] = json::array();
+    json operatingPoint = json();
+    operatingPoint["name"] = "Nominal";
+    operatingPoint["conditions"] = json();
+    operatingPoint["conditions"]["ambientTemperature"] = 42;
+
+    // Sinusoidal AC voltage, zero DC, no DC bias requested.
+    json windingExcitation = json();
+    windingExcitation["frequency"] = 200000;
+    windingExcitation["voltage"]["processed"]["label"] = WaveformLabel::SINUSOIDAL;
+    windingExcitation["voltage"]["processed"]["offset"] = 0;
+    windingExcitation["voltage"]["processed"]["peakToPeak"] = 2000;
+    // Pre-populated inductor current with zero DC component. This is what
+    // turns on the V+I path through is_continuously_conducting_power in the
+    // bug scenario.
+    windingExcitation["current"]["processed"]["label"] = WaveformLabel::SINUSOIDAL;
+    windingExcitation["current"]["processed"]["offset"] = 0;
+    windingExcitation["current"]["processed"]["peakToPeak"] = 2;
+    operatingPoint["excitationsPerWinding"] = json::array();
+    operatingPoint["excitationsPerWinding"].push_back(windingExcitation);
+    inputsJson["operatingPoints"].push_back(operatingPoint);
+
+    inputsJson["designRequirements"] = json();
+    inputsJson["designRequirements"]["magnetizingInductance"]["nominal"] = 100e-6;
+    inputsJson["designRequirements"]["turnsRatios"] = json::array();
+
+    OpenMagnetics::Inputs inputs(inputsJson);
+    auto excitation = inputs.get_operating_points()[0].get_excitations_per_winding()[0];
+    REQUIRE(excitation.get_magnetizing_current().has_value());
+    auto mcProcessed = excitation.get_magnetizing_current().value().get_processed().value();
+
+    double positivePeak = mcProcessed.get_positive_peak().value();
+    double negativePeak = mcProcessed.get_negative_peak().value();
+    double peak = mcProcessed.get_peak().value();
+    double peakToPeak = mcProcessed.get_peak_to_peak().value();
+    double offset = mcProcessed.get_offset();
+
+    // Bipolar centered: |+peak| ≈ |-peak|, midpoint ≈ 0.
+    double midpoint = (positivePeak + negativePeak) / 2;
+    double tolerance = 0.01 * peakToPeak;  // 1% of swing
+    REQUIRE_THAT(midpoint, Catch::Matchers::WithinAbs(0.0, tolerance));
+    REQUIRE_THAT(offset, Catch::Matchers::WithinAbs(0.0, tolerance));
+    REQUIRE(positivePeak > 0);
+    REQUIRE(negativePeak < 0);
+    // peak must be the half-swing (max of |+peak|, |-peak|), not the full PP.
+    REQUIRE_THAT(peak, Catch::Matchers::WithinRel(peakToPeak / 2, 0.02));
+}
+
 TEST_CASE("Test_Waveform_Coefficient_Sinusoidal", "[processor][inputs][smoke-test]") {
     json inputsJson;
 

tests/TestMagneticAdviser.cpp

@@ -3205,7 +3205,7 @@ namespace {
     TEST_CASE("Test_PlanarAdvise_Flow", "[adviser][planar][integration]") {
         try {
             // Load inputs from JSON file
-            std::ifstream file("tests/testData/planar_advise.json");
+            std::ifstream file(OpenMagneticsTesting::get_test_data_path(std::source_location::current(), "planar_advise.json"));
             REQUIRE(file.is_open());
 
             json j;
@@ -3354,7 +3354,7 @@ namespace {
 TEST_CASE("Test_Planar_CoilAdviser_From_Full_MAS", "[adviser][planar][coil][full-mas]") {
     try {
         // Load inputs from extracted JSON file (cleaned from full MAS)
-        std::ifstream file("tests/testData/planar_advise_from_mas_inputs.json");
+        std::ifstream file(OpenMagneticsTesting::get_test_data_path(std::source_location::current(), "planar_advise_from_mas_inputs.json"));
         REQUIRE(file.is_open());
 
         json j;